Debt - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	1 Months Ended		3 Months Ended	60 Months Ended	1 Months Ended
	Jan. 07, 2014	Nov. 30, 2006	Mar. 17, 2014	Mar. 31, 2015	Feb. 27, 2020	Apr. 30, 2015	Feb. 27, 2015	Jan. 07, 2013	Nov. 13, 2006	Dec. 31, 2013	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2010	Mar. 23, 2015	May 04, 2015
Line of Credit Facility, Maximum Borrowing Capacity							$ 2,500,000,000
line of credit available increase to credit facility							1,000,000,000
Convertible Senior Notes 2013
Senior Notes									1,725,000,000
Stated interest rate									1.75%
Cash payment to noteholders for outstanding principal of converted Notes	1,700,000,000
Shares issued to noteholders for the excess of the conversion value over the principal amount of converted Notes (in shares)	35
Value of the conversion value over the principal amount of converted Notes	858,000,000
Observation period	20 days
Convertible conversion ratio	62.6978
Conversion premium	26.50%
Conversion price per share								$ 15.95
Purchased Options
Purchased Options Remaining										108
Purchased options shares received	35
Sold Warrants
Incremental common shares attributable to call options and warrants		215
Common stock at an exercise price		$ 19.55							$ 19.31
Proceeds from issuance of warrants		391,000,000
Conversion premium based on the closing price		53.00%
Closing price per share									$ 12.61
Warrant
Warrants exercised			109,000,000
Exercised Warrants
Shares issues for exercised warrants			29
Long-term Debt
Unamortized discount				5,000,000
Effective interest rate				2.55%
Long-term Debt
Long term debt, aggregate principal											5,500,000,000
Interest Rate Swap
Aggregate notional amount of interest rate swap contracts designated as cash flow hedges													900,000,000
Losses on swaps at time of settlement, deferred												176,000,000
Losses reclassified from other comprehensive income and recognized as interest expense				6,000,000
Commercial Paper [Member]
Commercial Paper Maximum Borrowing Amount														2,500,000,000
Short-term Debt, Terms				The Commercial Paper will have maturities of up to 397 days from the date of issue
Scenario, Forecast
Line of Credit Facility, Expiration Date					Feb. 27, 2020
Line of Credit Facility, Description					At our option, subject to certain conditions, any loan under the Credit Agreement will bear interest at a rate equal to, either (i) the LIBOR Rate or (ii) the Base Rate (defined as the highest of (a) the Federal Funds rate plus 0.50%, (b) Citibank, N.A.’s “prime rate” as announced from time to time, or (c) one-month LIBOR plus 1.00%), plus, in each case the Applicable Margin, as defined in the Credit Agreement
Subsequent Event | Commercial Paper [Member]
Proceeds from Issuance of Commercial Paper															$ 950,000,000
Short-term Debt, Weighted Average Interest Rate						0.1558%
Subsequent Event | Minimum | Commercial Paper [Member]
Short-term Debt, Terms						P0Y0M21D
Subsequent Event | Maximum | Commercial Paper [Member]
Short-term Debt, Terms						P0Y0M59D